Oxidizing hydrocarbons



Patented Mar. 1?, i942 OXIDIZING HYDROCARBONS Clyde 0. Henkc, Wilmington, Del., and Roland G. Be E. I. mington,

No Drawing.

nner, Carneys Point, N. J., assignors to du Pont de Nemours & Company, Wil- Del., a corporation of Delaware Application June 8, 1940,

Serial No. 339,496

20 Claims. (01. 2eo 5z4) This invention relates to methods of oxidizing hydrocarbons and particularly to the catalytic oxidation of hydrocarbons in the liquid phase with oxygen-containing gases.

It has been proposed to produce aromatic carboxylic acids by oxidizing alkyl substituted aromatic compounds in the liquid phase by an oxygen-containing gas, employing a cobalt catalyst. D. J. Loder, in application Serial No, 235,578 filed October 18, 1938, has particularly disclosed a method whereby alkyl substituted aromatic compounds in a suitable solvent are oxidized in the liquid phase by means of an oxygencontaining gas in the presence of a cobalt catalyst at high temperatures. The production of carboxylic acid by these methods has been seriously handicapped bythe fact that the oxida-- tion mass is extremely corrosive. In many instances, it has been necessary to employ equipment lined with expensive materials such as tan talum and other costly acid-resistant materials in order to carry out the process in a practicable manner. The use of such expensive metals has materially increased the cost of carrying out the process and of the products produced thereby. Accordingly, it has become important to discover less expensive materials of which to make the equipment. Chromium-bearing steels, especially those containing small amounts of molybdenum, will resist corrosion by the oxidation masses in such processes. Howeuer, it has been found that such chromium-bearing steels exert an inhibitive effect on the process greatly decreasing the speed of the reaction and the yields obtained thereby.

It is an object of the .present invention to provide an economical and practical method for oxidizing alkyl substituted hydrocarbons in the liquid phase with oxygen-containing gases and in t e presence of a cobalt catalyst to produce aromatic carboxylic acids. Another object is to provide a method of carrying out such oxidation reactions in equipment composed of chromiumbearing steels in an economical and practicable manner obtaining relatively high yields of the desired carboxylic acids. A further object is to provide a method for carrying out such an oxidation process in a vessel composed of a chromlum-bearing steel carrying out such reaction in the presence of a compound which will counteract the inhibitive efiect of the chromiumbearing steel. A still further object is to provide an improvement over the process described by Loder, in application Serial No. 235,578, hereinbefore referred to, modifying such process of Loder by carrying it out in a chromium-bearing.

steel vesselin thepresence of compounds which The above and other objects may be accom; plished in accordance with our invention whichcomprises producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent, at temperatures of from about 150 C. to about 250 0., wherein the oxidation is catalyzed by a cobalt oxidation catalyst, in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble compound of a metal of the group of lead and barium. We have found that, while chromium-bearing steels have an inhibitive efiect on the oxidation of alkyl benzenes catalyzed by a cobalt catalyst, if a small amount of an acetic acid soluble compound of lead or barium is present during the reaction, such compounds of lead and barium counteract the inhibitive effect of the chromium-bearing steel and make it possible to obtain relatively high yields of the carboxylic acids.

By the term "alkyl benzene, we mean aromatic hydrocarbons consisting of a single benzene ring having substituted thereon one or more alkyl groups. By an alkyl group, we mean an aliphatic hydrocarbon group or radical. By a lower aliphatic acid, we mean one which contains from 1 to 6 carbon atoms and which, except for a single carboxyl group, consists of carbon and hydrogen. By the term acetic acid soluble," in referring to the lead and barium com-pounds, we mean that such compounds are soluble to the extent of at least 0.0001% in acetic acid at C.

The amount of lead or barium compound to be employed may 'be widely varied and will depend primarily upon the composition of the chromium-bearing steel and to a lesser extent on the time and temperature of oxidation. Accordingly, it is not possible to give the best proportions for use in all cases. However, We have found that from about 0.01% to about 4%, based on the alkyl benzene, will be satisfactory in most cases. After the lead or barium compound has been employed in one batch, its efiect will persist in subsequent batches so that several more batches of the carboxylic acid may be produced in the same equipment without the addition of further amounts of the lead or barium compound. Also, it is possible, afterone batch has been produced, to employ smaller amounts of the lead and barium compounds in subsequent batches in order to maintain the full effect of such compounds.

In order to illustrate our invention more clearly. the preferred modes of carrying the same into effect and the advantageous results to be obtained thereby, the following examples are given:

Example I In an apparatus, equipped with a glass liner, a solution, containing 100 parts toluene, 80 parts acetic acid and 4 .parts cobaltous acetate, was agitated at 180 to 200 C. under 200 to 300 lbs. oxygen pressure. Oxygen was absorbed rapidly and about 40% of the toluene was converted to benzoic acid in about 1 hour. Small amounts of benzaldehyde and benzyl alcohol were also formed.

With the same materials in the presence of 0.2 part chromium acetate, less than 5% of the toluene was converted to benzoic acid, under similar conditions, in one hour. In the presence of 0.2 part chromium acetate and 1 part lead acetate or 1 part barium acetate, 35 to 40% of the toluene was converted to benzoic acid in one hour.

Example II Into a bomb, made of stainless steel which contained about 18% chromium and 8% nickel, was charged 100 parts of toluene, 80 parts acetic acid and 4 parts cobaltous acetate. The solution was agitated at 190 to 205 C. under 250 to 300 lbs. oxygen pressure until the absorption of oxygen stopped. About 10% of the toluene was converted to benzoic'acid. With a similar charge in the presence of 4 parts lead acetate, a conversion of about was obtained under the same conditions.

Example III Into a bomb, made of stainless steel which contained about 17% chromium, 10% nickel and 2.7% molybdenum, was charged 100 parts toluene, 80 parts acetic acid, and 4 parts cobaltous acetate. The oxidation was carried out as in Example II and a conversion of to of toluene to benzoic acid was obtained. With a similar charge in the presence of 0.01 part lead acetate, a conversion of 45 to 50% was secured.

It will be understood that the above examples are given merely for illustrative purposes and that our invention is not to be limited to the specific embodiments described therein. Many variations and modifications may be made in such process without departing from the spirit of our invention. For example, the pressures employed may be widely varied and will be limited only by the strength of the equipment. Preferably, the process will be carried out at pressures above the vapor pressure of the alkyl benzene and within the non-explosive limits, in other words, at pressures at which the relative concentration of vapors of the alkyl benzene in the oxygen gas are not such as to produce an explosive mixture.

While the process is particularly adapted to the production of benzoic acid from toluene, it is also applicable to the preparation of other aromatic carboxylic acids from alkyl benzenes, particularly those included in the application of Loder, hereinbefore referred to. For example, ethyl benzene was satisfactorily oxidized to acetophenone and benzoic acid in chromium-bearing steel equipment in the presence of lead acetate.

Similarly, a commercial mixture of xylenes was satisfactorily oxidized to toluic acids.

While cobaltous acetate will preferably be employed as a catalyst, other well known cobalt oxidation catalysts may be employed and particularly those described by Loder in his application above referred to. Also the cobalt catalysts may be used in admixture with other catalysts or catalyst promoters.

While acetic acid is the preferred solvent, other lower aliphatic acids, such as propionic acid and butyric acid may be suitable.

The preferred compounds of lead and barium will be the acetates. However, other compounds of these metals, which are soluble to the extent of at least 0.0001 in acetic acid at C., or which react with acetic acid to form acetates, will be suitable. some of such compounds of lead and barium are:

Lead formate Barium formate Lead propionate Barium propionate Lead butyrate Barium butyrate Lead oleate Barium oleate Lead stearate Barium stearate Lead oxalate Barium oxalate Lead chloride Barium chloride Lead bromide Barium bromide Lead iodide Barium iodide Lead benzoate Barium benzoate Lead carbonate Barium carbonate Lead borate Barium borate Lead oxide Barium oxide Lead hydroxide Barium hydroxide It will thus be appreciated that, by our invention, we have made it possible to carry out oxidations of alkyl benzenes in the liquid' ase and in the presence of cobalt catalysts in equipment made of chromium-bearing steels which is practical for operations on a large commercial scale. We have made it possible to avoid the use of expensive lining materials, thereby effecting large economies in carrying out the process and mak-v ing it possible to produce the products in a more economical and practical manner.

We claim:

1. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a ,lower aliphatic acid as a solvent at temperatures of from about C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-rbearing steel and. in the presence of an acetic acid soluble compound of a metal of the group consisting of lead and barium.

2. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble compound of lead.

3. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble salt of lead.

4. In the process of producing aromatic carboxyiic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble lead salt of a carboxylic acid.

5. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble lead salt of an unsubstituted aliphatic acid.

6. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble lead salt of a lower aliphatic acid.

7. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about-250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of lead acetate.

8. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble compound of barium.

9. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble salt of barium.

10. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of an acetic acid soluble barium salt of a carboxylic acid.

11. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence or an acetic acid soluble barium salt of a lower aliphatic acid.

12. In the process of producing aromatic carboxylic acids by oxidizing an alkyl benzene in the liquid phase in a lower aliphatic acid-as a solvent at temperatures ofirom about C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromium-bearing steel and in the presence of barium acetate.

13. In the process of producing benzoic acid by oxidizing toluene in the liquid phase in acetic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromiumbearing steel and in the presence of an acetic acid soluble compound of a metal of the group consisting of lead and barium.

14. In the process of of producing benzoic acid by oxidizing toluene in the liquid phase in acetic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of chromiumbearing steel and in the presence of an acetic acid soluble compound of lead. 15. In the process of producing benzoic acid by oxidizing toluene in the liquid phase in acetic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromiumbearing steel and in the presence of an acetic acid soluble salt of lead.

16. In the process of producing benzoic acid by oxidizing toluene in the liquid phase in acetic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of chromiumbearing steel and in the presence of an acetic acid soluble lead salt of an aliphatic acid.

17. In the process of producing benzoic acid by oxidizing toluene in the liquid phase in acetic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of "a chromiumbearing steel and in the presence of lead acetate.

18. In the process of producing benzoic acid by oxidizing toluene in the liquid phasein acetic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromiumbearing steel and in the presence of an acetic acid soluble compound of barium.

19. In the process of producing benzoic acid by oxidizing toluene in the liquid phase in acetic acid as a solvent at temperatures of from about 150 C. to about 250 C. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the improvement which comprises carrying out the oxidation in a vessel composed of a chromiumbearing steel and in the presence or an acetic acid soluble salt of barium.

20. In the process of producing benzoic acid by oxidizing toluene in the liquid phase in acetic acid as a solvent at temperatures oi from about 150 C. to about 250 0. wherein the oxidation is catalyzed by a cobalt oxidation catalyst, the immovement which comprises carrying out the oxidation in a vessel composed of a chromiumbearing steel and in the presence of an acetic acid soluble barium salt of an aliphatic acid.

CLYDE 0. mm. ROLAND G. 31mm. 

